Ambassador Yosef Tekoah, Israel’s permanent representative to the UN, challenged yesterday the Syrian representative to the UN, Mr. George Tomeh, to produce evidence of his charge on Feb. 5 that Israel was mistreating Arab prisoners. In a letter to UN Secretary General U Thant, Mr. Tekoah stated that Mr. Tomeh’s latest charge, like his one on Jan. 23, “does not produce a single shred of evidence” to confirm his contention. Mr. Tekoah stated that these charges were a smoke screen to draw attention away from “the farcical situation created by membership on the Security Council by a government which persists in its policy of violating Charter provisions, the cease-fire and the Security Council’s resolution calling for an agreement on a just and lasting peace with Israel.”